Such devices are also known as “tremolo devices”, “vibrato devices” or simply “tremolo” or “vibrato”, among other terms.
For a better understanding of the invention and to provide greater clarity thereof, the following terms are defined below:                The term “bridge of the guitar” means the part located in the lower part of the top or body of the guitar that holds the strings.        The term “saddle” means a part located on top of the bridge of the guitar, on which the strings sit or are supported and from which the vibration of the strings begins. In addition, the saddle transmits the vibrations of the strings to the bridge and the body. The part known in English as the “saddle” is also known in Spanish as “selleta”, “silleta”, “sillin” or “asiento”.        
Tremolo or vibrato devices usually consist of a bridge unit that is movable about an axis and upon which are arranged the saddles corresponding to each string of the guitar, said bridge unit comprising an arm that acts as a lever upon which the guitarist can apply pressure in order to move said bridge unit and thereby alter the tension of the strings. Tremolo devices tend to have one or more springs that act directly on the actuation mechanism via the lever, facilitating the return of the lever to the neutral position.
However, many bridge units in the state of the art are bulky units of considerable weight, and are therefore very troublesome for the guitarist. In addition, many of these units are not suitable for all types of guitar and, in many cases, require at least one perforation to be made in the body of the guitar in order to incorporate the spring mechanism associated with said bridge units. Moreover, many tremolo units fail to maintain a constant equilibrium between the tension exerted by the strings and the opposing tension exerted by the springs, leading to loss of the tuning of the guitar strings.